Use a different service provider, or travel on those tube lines where mobile network services are now available underground, @Andre79. 

https://tfl.gov.uk/campaign/station-wifi

Tried logging in other networks but I get this sign in page with them all.

Unfortunately @Andre79, to use THREE_WIFI your handset would need to be using an active SIM from Three UK.

Likewise for EE, O2 and Vodafone.
 

Thanks, Andewhite. So am I right in thinking ID customers can't access free WiFi due to not being a service provider for tfl?

Hey there @Andre79, welcome to Community!

Please read the following Community page for further information:

https://community.idmobile.co.uk/articles-and-competitions-45/stay-connected-on-the-london-underground-54127#:~:text=How%20do%20I%20connect%20to,if%20you%20were%20still%20overground.

Thank you,

Tyler

Some piggyback networks do let you onto the Wifi. Eg SMARTY customers can connect to the Three Wifi service on the Underground. Lebara customers can connect onto the Vodafone Wifi.

Unfortunately iD Mobile does not give access (although in some cases it lets you on anyway, I am no longer with iD but I used to be able to connect anyway, not sure why...)

Hey there @tom12, thank you for the further advice for our customers.

Kind regards,

Tyler

Tried logging in other networks but I get this sign in page with them all.

 

Try changing EAP method to AKA. 

Other Three MVNO’s can use the wifi service provided by TFL via sim authorization, so technically it is possible for ID to do the same. I presume ID would have to pay a fee for the privilege..